VoIP Hacks

Colophon

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The tool on the cover of VoIP Hacks is a Morse code tapper. Also known as a telegraph key, this electrical switching device is used to send Morse code over electrical wires.

The old-school variety of telegraph key, glamorized in many classic films, was the straight key, a simple contraption fashioned from a bar with a knob fastened atop one end. When the knob was depressed, the bar completed an electrical circuit, and current flowed through the telegraph wires. By rapidly forming and breaking this circuit, telegraphers could transmit a series of signals, conventionally known as “dits” and “dahs” (or, more colloquially, “dots” and “dashes”), which spurred an electromagnet on the receiving end to produce clicking noises that could be recorded to paper tape or deciphered directly by skilled operators.

Unfortunately, design constraints of the straight key limited its transmission capabilities to a mere 20 words per minute. Additionally, the vigorous “brass pounding” required of early telegraphers sometimes led to a repetitive stress injury called glass arm, known today as carpal tunnel syndrome.

Sanders Kleinfeld was the production editor, and Audrey Doyle was the copyeditor for VoIP Hacks. Sanders Kleinfeld proofread the book. Philip ...